Modern electronic components, such as integrated circuits, processor chips, and power supplies are typically mounted on circuit boards, PC boards, or telecommunication boards and often produce significant quantities of heat which can damage the component itself and/or other adjacent components. Accordingly, heat sinks are used to cool and dissipate heat from such components.
Heat sinks are often attached to the top of the electronic component to remove heat from the component by conduction. For heat transfer by conduction, the predominant factors include the thermal conductive properties of the material of the heat sink, the cross sectional area of the heat sink, and the thickness of the heat sink in the main direction of the heat flow.
For a homogenous material, heat transfer by conduction in any direction is dictated by the relationship:                               q          x                =                              -                          kA              x                                ⁢                                    ⅆ              T                                      ⅆ              x                                                          (        1        )            where x is the direction of heat flux, k is the thermal conductivity of the heat sink material, Ax is the cross-sectional area perpendicular to the heat transfer direction, and       ⅆ    T        ⅆ    x  is the rate of temperature change in the heat transfer direction. For conceptual convenience, consider a one-dimensional heat conduction situation for which Eq. 1 simplifies to                               q          L                =                  kA          ⁢                                           ⁢                                    Δ              ⁢                                                           ⁢              T                        L                                              (        2        )            where L is the thickness of the material in the main direction of heat flow. This equation shows that the heat transfer rate is directly proportional to the cross-sectional area of the heat sink and inversely proportional to the path traversed by the heat flux.
Heat sinks themselves are cooled by a process known as heat transfer by convection. For this process of heat removal, which relies on a flow of air around the heat sink, the total surface area subject to an air flow is the critical factor.
Typical prior art heat sinks incorporate a body with a constant uniform thickness and therefore a constant uniform cross sectional area. One problem with this design is that the heat sink itself is not cooled uniformly because the edges of the sink have a greater surface area exposed to ambient air than the interior portion, and thus the edges cool more efficiently by convection than the interior portion. Because the heat transfer by conduction is uniform throughout the heat sink because of the constant cross-sectional area of the heat sink, any component attached to the heat sink is cooled more on the outside edges than the interior portion, leading to uneven cooling and heat dissipation of the component. Warping, cracking, or malfunctioning of the electronic component is often the result.
Further, prior art heat sinks are not aerodynamically efficient because the flat square shape of the heat sink body obstructs air flow passing.
Some prior art heat sinks include fins to enhance the convective cooling efficiency. The fins increase the total surface area of the heat sink and therefore increase the overall heat transfer by convection. However, prior art fin designs typically employ upstanding parallel fins with rectangular channels between adjacent fins. Alternatively, some prior art heat sinks use cylindrical “pin-fins”. Both of these fin designs, however, have several disadvantages.
For parallel fin designs, the square channel design blocks and obstructs air flow thereby increasing air flow resistance, lowering air flow velocity, and reducing the convective cooling ability of the heat sink.
Also, parallel fin designs with rectangular channels between the adjacent fins is inefficient because each upstanding parallel fin projects radiating air toward all the adjacent fins which partially heats the adjacent fins and reduces the cooling efficiency of the heat sink.
Cylindrical “pin-fin” heat sinks also suffer from the same problem because heat is projected 360° from each cylindrical pin-fin toward all adjacent fins.
In addition, the square or cylindrical pin-fin designs do not provide the maximum surface area to fin density and footprint to maximize convective cooling of the heat sink.